Connect Modem or existing Routers and Airport via Ethernet cable

Apple Airport Extreme not only comes with beautiful design but also provides mac users with impressed Wifi performance improvement and security. A common problem you might encounter is how to connect the Apple Airport Extreme to your Modem or existing Routers via Airport ethernet cable. Look at our following instruction to do.

To avoid any confused things, my context is that I have been using Wireless from my Airport extreme. My Apple airport is connected to a Cisco Router which is plugged into the main router (Modem) via cable.

To check the IP-address of the ethernet interface and the Subnet mask of the Airport Extreme which is connected to my laptop directly, access System Preference > Network > Select WiFi net work name on the left side > Click on Advanced button.

From the NetWork window coming up, select TCP/IP tab, you will be able to see the router ip address and the subnet mask:

For example, my Airport Router ip address is 192.168.1.1 (yours should be 10.0.1.1 or 192.168.2.254) and the Subnet Mask is 255.255.255.0.

My computer will be lost if there are 3 identical ip addresses of the modem, Cisco router and the Apple Airport. So, what I need to do is that Just enter the setup and manually configure an IP-address for the ethernet interface of the Airport Extreme in the same private address range as the ethernet interface in the Cisco router and the Modem.

More specifically, If the IP-address of the ethernet interface (The modem) is 192.168.1.1 and the Subnet mask is 255.255.255.0, I need to assign 192.168.1.2 Subnet mask 255.255.255.0 to the ethernet interface (Cisco router) and 192.168.1.3 Subnet mask 255.255.255.0 to the Apple Airport Extreme.